linux-kernel - Re: [PATCH 1/2] mm: vmemmap: x86: add vmemmap

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Date:	Mon, 08 Apr 2013 18:23:16 +0800
From:	Lin Feng <linfeng@...fujitsu.com>
To:	akpm@...ux-foundation.org, cl@...ux.com
CC:	Lin Feng <linfeng@...fujitsu.com>, tglx@...utronix.de,
	mingo@...hat.com, hpa@...or.com, yinghai@...nel.org,
	catalin.marinas@....com, will.deacon@....com, arnd@...db.de,
	tony@...mide.com, ben@...adent.org.uk,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	x86@...nel.org, linux-mm@...ck.org, isimatu.yasuaki@...fujitsu.com
Subject: Re: [PATCH 1/2] mm: vmemmap: x86: add vmemmap_verify check for hot-add
 node case

Hi all,

On 04/08/2013 05:56 PM, Lin Feng wrote:
> diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
> index 474e28f..e2a7277 100644
> --- a/arch/x86/mm/init_64.c
> +++ b/arch/x86/mm/init_64.c
> @@ -1318,6 +1318,8 @@ vmemmap_populate(struct page *start_page, unsigned long size, int node)
>  			if (!p)
>  				return -ENOMEM;
>  
> +			vmemmap_verify((pte_t *)p, node, addr, addr + PAGE_SIZE);
> +
>  			addr_end = addr + PAGE_SIZE;
>  			p_end = p + PAGE_SIZE;
>  		} else {
IIUC it seems that the original 'p_end = p + PAGE_SIZE' assignment is buggy, because:

1309                 if (!cpu_has_pse) {
1310                         next = (addr + PAGE_SIZE) & PAGE_MASK;
1311                         pmd = vmemmap_pmd_populate(pud, addr, node);
1312 
1313                         if (!pmd)
1314                                 return -ENOMEM;
1315 
1316                         p = vmemmap_pte_populate(pmd, addr, node);
1317 
1318                         if (!p)
1319                                 return -ENOMEM;
1320 
1321                         addr_end = addr + PAGE_SIZE;
1322                         p_end = p + PAGE_SIZE;

The return value of vmemmap_pte_populate() is the virtual address of pte, not the allocated
virtual address, which is different from vmemmap_alloc_block_buf() in cpu_has_pse case, so
the addition PAGE_SIZE in !cpu_has_pse case is nonsense.

Or am I missing something?

thanks,
linfeng
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